<?php

/**
 * @file
 * Parser functions for the aggregator module.
 */

/**
 * Implements hook_aggregator_parse_info().
 */
function aggregator_aggregator_parse_info() {
	return array(
			'title' => t('Default parser'),
			'description' => t('Parses RSS, Atom and RDF feeds.'),
	);
}

/**
 * Implements hook_aggregator_parse().
 */
function aggregator_aggregator_parse($feed) {
	global $channel, $image;

	// Filter the input data.
	if (aggregator_parse_feed($feed->source_string, $feed)) {
		$modified = empty($feed->http_headers['last-modified']) ? 0 : strtotime($feed->http_headers['last-modified']);

		// Prepare the channel data.
		foreach ($channel as $key => $value) {
			$channel[$key] = trim($value);
		}

		// Prepare the image data (if any).
		foreach ($image as $key => $value) {
			$image[$key] = trim($value);
		}

		$etag = empty($feed->http_headers['etag']) ? '' : $feed->http_headers['etag'];

		// Add parsed data to the feed object.
		$feed->link = !empty($channel['link']) ? $channel['link'] : '';
		$feed->description = !empty($channel['description']) ? $channel['description'] : '';
		$feed->image = !empty($image['url']) ? $image['url'] : '';
		$feed->etag = $etag;
		$feed->modified = $modified;

		// Clear the cache.
		cache_clear_all();

		return TRUE;
	}

	return FALSE;
}

/**
 * Parses a feed and stores its items.
 *
 * @param $data
 *   The feed data.
 * @param $feed
 *   An object describing the feed to be parsed.
 *
 * @return
 *   FALSE on error, TRUE otherwise.
 */
function aggregator_parse_feed(&$data, $feed) {
	global $items, $image, $channel;

	// Unset the global variables before we use them.
	unset($GLOBALS['element'], $GLOBALS['item'], $GLOBALS['tag']);
	$items = array();
	$image = array();
	$channel = array();

	// Parse the data.
	$xml_parser = drupal_xml_parser_create($data);
	xml_set_element_handler($xml_parser, 'aggregator_element_start', 'aggregator_element_end');
	xml_set_character_data_handler($xml_parser, 'aggregator_element_data');

	if (!xml_parse($xml_parser, $data, 1)) {
		watchdog('aggregator', 'The feed from %site seems to be broken, due to an error "%error" on line %line.', array('%site' => $feed->title, '%error' => xml_error_string(xml_get_error_code($xml_parser)), '%line' => xml_get_current_line_number($xml_parser)), WATCHDOG_WARNING);
		drupal_set_message(t('The feed from %site seems to be broken, because of error "%error" on line %line.', array('%site' => $feed->title, '%error' => xml_error_string(xml_get_error_code($xml_parser)), '%line' => xml_get_current_line_number($xml_parser))), 'error');
		return FALSE;
	}
	xml_parser_free($xml_parser);

	// We reverse the array such that we store the first item last, and the last
	// item first. In the database, the newest item should be at the top.
	$items = array_reverse($items);

	// Initialize items array.
	$feed->items = array();
	foreach ($items as $item) {

		// Prepare the item:
		foreach ($item as $key => $value) {
			$item[$key] = trim($value);
		}

		// Resolve the item's title. If no title is found, we use up to 40
		// characters of the description ending at a word boundary, but not
		// splitting potential entities.
		if (!empty($item['title'])) {
			$item['title'] = $item['title'];
		}
		elseif (!empty($item['description'])) {
			$item['title'] = preg_replace('/^(.*)[^\w;&].*?$/', "\\1", truncate_utf8($item['description'], 40));
		}
		else {
			$item['title'] = '';
		}

		// Resolve the items link.
		if (!empty($item['link'])) {
			$item['link'] = $item['link'];
		}
		else {
			$item['link'] = $feed->link;
		}

		// Atom feeds have an ID tag instead of a GUID tag.
		if (!isset($item['guid'])) {
			$item['guid'] = isset($item['id']) ? $item['id'] : '';
		}

		// Atom feeds have a content and/or summary tag instead of a description tag.
		if (!empty($item['content:encoded'])) {
			$item['description'] = $item['content:encoded'];
		}
		elseif (!empty($item['summary'])) {
			$item['description'] = $item['summary'];
		}
		elseif (!empty($item['content'])) {
			$item['description'] = $item['content'];
		}

		// Try to resolve and parse the item's publication date.
		$date = '';
		foreach (array('pubdate', 'dc:date', 'dcterms:issued', 'dcterms:created', 'dcterms:modified', 'issued', 'created', 'modified', 'published', 'updated') as $key) {
			if (!empty($item[$key])) {
				$date = $item[$key];
				break;
			}
		}

		$item['timestamp'] = strtotime($date);

		if ($item['timestamp'] === FALSE) {
			$item['timestamp'] = aggregator_parse_w3cdtf($date); // Aggregator_parse_w3cdtf() returns FALSE on failure.
		}

		// Resolve dc:creator tag as the item author if author tag is not set.
		if (empty($item['author']) && !empty($item['dc:creator'])) {
			$item['author'] = $item['dc:creator'];
		}

		$item += array('author' => '', 'description' => '');

		// Store on $feed object. This is where processors will look for parsed items.
		$feed->items[] = $item;
	}

	return TRUE;
}

/**
 * Performs an action when an opening tag is encountered.
 *
 * Callback function used by xml_parse() within aggregator_parse_feed().
 */
function aggregator_element_start($parser, $name, $attributes) {
	global $item, $element, $tag, $items, $channel;

	$name = strtolower($name);
	switch ($name) {
		case 'image':
		case 'textinput':
		case 'summary':
		case 'tagline':
		case 'subtitle':
		case 'logo':
		case 'info':
			$element = $name;
			break;
		case 'id':
		case 'content':
			if ($element != 'item') {
				$element = $name;
			}
		case 'link':
			// According to RFC 4287, link elements in Atom feeds without a 'rel'
			// attribute should be interpreted as though the relation type is
			// "alternate".
			if (!empty($attributes['HREF']) && (empty($attributes['REL']) || $attributes['REL'] == 'alternate')) {
				if ($element == 'item') {
					$items[$item]['link'] = $attributes['HREF'];
				}
				else {
					$channel['link'] = $attributes['HREF'];
				}
			}
			break;
		case 'item':
			$element = $name;
			$item += 1;
			break;
		case 'entry':
			$element = 'item';
			$item += 1;
			break;
	}

	$tag = $name;
}

/**
 * Performs an action when a closing tag is encountered.
 *
 * Callback function used by xml_parse() within aggregator_parse_feed().
 */
function aggregator_element_end($parser, $name) {
	global $element;

	switch ($name) {
		case 'image':
		case 'textinput':
		case 'item':
		case 'entry':
		case 'info':
			$element = '';
			break;
		case 'id':
		case 'content':
			if ($element == $name) {
				$element = '';
			}
	}
}

/**
 * Performs an action when data is encountered.
 *
 * Callback function used by xml_parse() within aggregator_parse_feed().
 */
function aggregator_element_data($parser, $data) {
	global $channel, $element, $items, $item, $image, $tag;
	$items += array($item => array());
	switch ($element) {
		case 'item':
			$items[$item] += array($tag => '');
			$items[$item][$tag] .= $data;
			break;
		case 'image':
		case 'logo':
			$image += array($tag => '');
			$image[$tag] .= $data;
			break;
		case 'link':
			if ($data) {
				$items[$item] += array($tag => '');
				$items[$item][$tag] .= $data;
			}
			break;
		case 'content':
			$items[$item] += array('content' => '');
			$items[$item]['content'] .= $data;
			break;
		case 'summary':
			$items[$item] += array('summary' => '');
			$items[$item]['summary'] .= $data;
			break;
		case 'tagline':
		case 'subtitle':
			$channel += array('description' => '');
			$channel['description'] .= $data;
			break;
		case 'info':
		case 'id':
		case 'textinput':
			// The sub-element is not supported. However, we must recognize
			// it or its contents will end up in the item array.
			break;
		default:
			$channel += array($tag => '');
			$channel[$tag] .= $data;
	}
}

/**
 * Parses the W3C date/time format, a subset of ISO 8601.
 *
 * PHP date parsing functions do not handle this format. See
 * http://www.w3.org/TR/NOTE-datetime for more information. Originally from
 * MagpieRSS (http://magpierss.sourceforge.net/).
 *
 * @param $date_str
 *   A string with a potentially W3C DTF date.
 *
 * @return
 *   A timestamp if parsed successfully or FALSE if not.
 */
function aggregator_parse_w3cdtf($date_str) {
	if (preg_match('/(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})(:(\d{2}))?(?:([-+])(\d{2}):?(\d{2})|(Z))?/', $date_str, $match)) {
		list($year, $month, $day, $hours, $minutes, $seconds) = array($match[1], $match[2], $match[3], $match[4], $match[5], $match[6]);
		// Calculate the epoch for current date assuming GMT.
		$epoch = gmmktime($hours, $minutes, $seconds, $month, $day, $year);
		if ($match[10] != 'Z') { // Z is zulu time, aka GMT
			list($tz_mod, $tz_hour, $tz_min) = array($match[8], $match[9], $match[10]);
			// Zero out the variables.
			if (!$tz_hour) {
				$tz_hour = 0;
			}
			if (!$tz_min) {
				$tz_min = 0;
			}
			$offset_secs = (($tz_hour * 60) + $tz_min) * 60;
			// Is timezone ahead of GMT?  If yes, subtract offset.
			if ($tz_mod == '+') {
				$offset_secs *= -1;
			}
			$epoch += $offset_secs;
		}
		return $epoch;
	}
	else {
		return FALSE;
	}
}
